Ruthenium-containing catalysts for decomposing ammonia into nitrogen and hydrogen which may for example be used in low-temperature fuel cells have conventionally been prepared according to the method described in U.S. Pat. No. 5,055,282, herein incorporated in its entirety by reference, namely by introducing granules of Al2O3 into an aqueous solution of RuCl3 and an alkali or alkaline earth nitrate, calcining the solid product and reducing the ruthenium in a stream of hydrogen for three hours at 400° C.
Accordingly, the alumina granules are first impregnated with RuCl3, and then the ruthenium ions on the impregnated granules are reduced.
According to the cited patent the ammonia conversion is quantitative already at 500° C.
This preparation method of a Al2O3-supported Ru catalyst for decomposing ammonia is energy and time consuming, since hydrogen has to be streamed over the RuCl3/Al2O3 for 3 hours at 400° C.
Furthermore, catalysts prepared according to that method have a drawback: Chloride ions can be captured in pores of the alumina granules, which deteriorates the catalyst performance during use at the high temperatures required for cracking ammonia.
At that temperatures there is also a propensity of the ruthenium/alkali or alkaline earth metal clusters on the alumina to aggregate during prolonged use at high temperatures.